my $info1 = grok_file $file1;
  my $info2 = grok_file $file2;
MODULE:
  while ( my ($module, $nets_href) = each %$info1 )
  {
      unless ( $info2->{$module} )
      {
          warn "$file2 has no module $module";
          next MODULE;
      }

    NET:
      while ( my ($net, $gates_href) = each %$nets_href )
      {
          unless ( $info2->{$module}->{$net} )
          {
              warn "$file2 has no net $module/$net";
              next NET;
          }

        GATE:
          while ( my ( $gate, $href1 ) = each %$gates_href )
          {
              my $href2 = $info2->{$module}->{$net}->{$gate};
              unless ( $href2 )
              {
                  warn "$file2 has no gate $module/$net/$gate";
                  next GATE;
              }

              diff_gates "$module/$net/$gate", $href1, $href2;
          } # GATE

      } # NET

  } # MODULE